This invention relates to the improvement of titanium nitride films, particularly those used in shielding windows from excessive heat gain during warm weather.
It has also been proposed in U.S. Pat. No. 3,885,855 to produce solar control films by reactive sputtering of the nitrides, carbides or borides of the metals titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, or tungsten. While effective optical properties were known for some of these materials, any large-scale production of architectural glass by the vacuum electrical method of reactive sputtering would be rather slow and expensive.
Control of the solar energy coming into windows is important in maintaining comfortable indoor conditions in warm climates. Solar control has been achieved commonly by adding light-responsive colorant material to the glass. Tinting of glass in this way has disadvantages in production, however, since a long time may be required to change shades. More recently, reflecting and absorbing films have been applied to clear glass, to achieve solar control. Reflection of unwanted radiation is more efficient than absorption, since reflection eliminates the radiation completely, whereas part of the absorbed heat is eventually carried into the building.
In U.S. Pat. No. 4,535,000 issued on Aug. 12, 1985, (incorporated herein by reference) Roy G. Gordon disclosed a rapid process for deposition of transparent solar screens of titanium nitride while avoiding haze and imperfections on the sheet being coated. Such problems could have been caused by premature, powder-forming condensation of reactants in reactor conduits.
There are a large number of other procedures and products characterized by the deposition of titanium nitride on substrates. Most of these relate to wear-resistant layers of the nitride which, because of their thickness, render the film opaque. All questions of light transmission or optical quality of such materials are not applicable to such materials and procedures.
The improvements in titanium nitride deposition procedures did not avoid some inherent problems in achieving broad acceptance of TiN as a glass-coating material in such markets as architectural glass. These problems included some susceptibility to mechanical and chemical attack and some limitations with respect to visual characteristics of TiN film. The invention described below arose out of work directed to the solving of these problems.